Conventionally, in mounting a pulser ring (wheel speed sensor ring) used in an ABS (Antilock Brake System) or the like on a wheel body of a wheel, there has been known a structure wherein the pulser ring is fixed to the wheel body by fastening together with a brake disc (see JP-A-2005-271666, for example).
In the above-mentioned conventional structure, there may be a case where a brake disc expands due to its own heat generation when a brake is used at high frequency and hence, the pulser ring also expands along with the expansion of the brake disc to which it is fixed. In this case, it is necessary to take a countermeasure to assure sensor accuracy, such as the reinforcement of the pulser ring. Hence, there arises a drawback that the miniaturization of the structure is difficult to achieve.